first off im relaively new to linux so im not 100% sure this will work but i think it does,
If you have some form of backup medium ready. Then either install another distro of linux or get a linux boot cd (there are a few disto's that you can make a linux bootable cd, one i have is called "dynebolic" however a friend burned it to disk for me so i have no idea where to get it, however a google should turn that up easy) you can then boot the comp with the other distro of linux and use it to copy the needed files (and i would have thought config files too) to your backup medium. Once youve done that you should be ok to to re-install linux from scratch.